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Equipment Discussions >> Mounts

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CMM
member


Reged: 09/29/10

Loc: Chandler, AZ, USA
OAG with a refractor and FF
      #4397648 - 02/19/11 06:26 PM

I'm thinking about using an OAG with my AT111 scope rather than using the AT72 as a guidescope due to flexure issues. The complication is that I'm using the AT2FF. With a back focus of 55 mm limitation on the field flattener, there seems to be no way to put an OAG and a FW between the FF and a CCD camera.

Does anybody use an OAG on a refractor with a field flattener? Are there FF with larger chip-to-flattener distances that are good for this sort of application?

-Carl


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CMM
member


Reged: 09/29/10

Loc: Chandler, AZ, USA
Re: OAG with a refractor and FF new [Re: CMM]
      #4397658 - 02/19/11 06:27 PM

I just realized I put this post in the mounts forum. Sorry.

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saadabbasi
Pooh-Bah


Reged: 08/23/09

Loc: 29N
Re: OAG with a refractor and FF new [Re: CMM]
      #4397677 - 02/19/11 06:36 PM

Why not put the AT2FF after the OAG?

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jmasin
Carpal Tunnel


Reged: 12/22/08

Loc: Murphy, TX (DFW)
Re: OAG with a refractor and FF new [Re: saadabbasi]
      #4398281 - 02/19/11 11:05 PM

CMM,

I'm sure they'll move this but there is an OAG out there with only 9mm of thickness. Google: TSOAG9T2


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LLEEGE
True Blue
*****

Reged: 03/03/05

Loc: Cloud-chester,NY
Re: OAG with a refractor and FF new [Re: jmasin]
      #4398982 - 02/20/11 10:15 AM

What OAG are you considering?

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CMM
member


Reged: 09/29/10

Loc: Chandler, AZ, USA
Re: OAG with a refractor and FF new [Re: LLEEGE]
      #4399041 - 02/20/11 11:01 AM

I've heard about the TS-9 OAG, but have heard mixed reviews - it can only be placed in 3 distinct orientations with respect to the imaging camera. At the moment I have a Celestron radial guider for my SCT, and I like the easy rotation capability of the guider.

As far as putting the AT2FF after the OAG - there are 2 reasons why I thought this might be problematic. The first is that the guide camera would have to be WAY out to be able to achieve focus at the same time as the imaging camera. The second reason is that I don't know how I would attach the AT2FF (that has a 2" barrel connection) to most OAG's that have T-thread outputs.

The main reason I posted the thread is that I was wondering if anyone actually did use an OAG with a refractor setup, and if so, how was it done.

-Carl


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saadabbasi
Pooh-Bah


Reged: 08/23/09

Loc: 29N
Re: OAG with a refractor and FF new [Re: CMM]
      #4399313 - 02/20/11 01:04 PM

I use a OAG with my Tak, but it doesn't need a field flattener.

I understand that you'll need to put the autoguider way out to achieve focus - I didn't realize this beforehand. As far as attaching the AT2FF is concerned, the Hutech OAG5 can be purchased with a 2" adapter (which connects to the camera side). The AT2FF should slide right in there.

Contact Hutech and Ted should be able to find all the parts you need. They have a very extensive library.


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CMM
member


Reged: 09/29/10

Loc: Chandler, AZ, USA
Re: OAG with a refractor and FF new [Re: saadabbasi]
      #4401141 - 02/21/11 09:16 AM

Thanks for the info!
-Carl


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DeanS
Post Laureate
*****

Reged: 07/12/05

Loc: Central Kentucky
Re: OAG with a refractor and FF new [Re: CMM]
      #4401157 - 02/21/11 09:23 AM

My Starlightxpress H18, SX filter wheel, SX OAG have a back focus of 56mm which is pretty close to what you need. Generally filters will add 1mm to the backfocus length so it could work for you. But have no idea of your current set up.

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